Adjustable induction coil for zone melting of semiconductor rods

ABSTRACT

A readily disassembleable and easily producible induction coil useful in crucible-free floating melt zone treatment of semiconductor rods comprised of a single or multi-turn induction coil provided with a separable ring-shaped insert which has onehalf thereof rigidly attached to an inner surface of the coil and another half separably attached to the first half with the end surfaces of the insert halves being located perpendicularly to the plane of the coil. A conduit is disposed within the insert for guiding a heat-exchange fluid therethrough.

United States Patent Keller 1 1 May 27, 1975 [54] ADJUSTABLE INDUCTION COIL FOR 2,419,116 4/1947 Cassen et a1 219/1079 ZONE MEL-TING 0F SEMICONDUCTOR 2,456,091 4/1947 Stevens et a1 219/1079 RODS 2,459,971 1/1949 Stanten 336/62 X 2,481,008 9/1949 Gagliardi et a1. 219/1079 [75] inventor: Wolfgang Keller, Munich, Germany 2,709,741 5/1955 Albrecht 336/62 X 3,110,793 11/1963 Worthington 219/1079 UX 1 1 Asslgfleei slemens Aktlengesellschafl, Beth" & 3,428,769 2/1969 Cizewski et al.... 219/1029 x Munich, Germany 3,534,198 10/1970 Miller 336/62 x Filed: Jan. 23 [974 3,593,242 7/1971 Andersson 336/62 121] App]. No.: 435,837 OREIGN PATENTS OR APPLICATIONS 1,002,388 8/1965 United Kingdom 336/62 Related U.S. Application Data [63] Continuation-impart of Ser. No. 309,420, Nov, 24, P i ary Examiner Thomag J, Kozma 1972.131" 3327917 Attorney, Agent, or Firm-Hill, Gross, Simpson, Van

Santen, Steadman, Chiara & Simpson [30] Foreign Application Priority Data Feb. 1, 1973 Germany 2304974 57 ABSTRACT 52 13.5. C1. 336/62; 219/1079; 336/223; easly pr9duc'ble 336/232 tion C011 use 1.11 111 crucible-free float ng melt zone H In 27/28 treatment of semiconductor rods comprised of a single [58] Field of Search 336/62, 232, 223-, 9. i prov'ded /1 ring-shaped insert WhlCh has one-half thereof rigidly 219/1079 attached to an Inner surface of the coil and another half separably attached to the first half with the end 156] References Cited surfaces of the insert halves being located perpendicu- UNITED STATES PATENTS larly to the plane of the coil. A conduit is disposed 1.335395 4/1920 Hughes u 336/62 within the insert for guiding a heat-exchange fluid 2,264,301 12/1941 Denneen et a1 219/1079 X therethrough 2,266,176 12/1941 Denneen et a1 219/1079 X 2.404.987 7/1946 Rudd 219/1079 X 4 Claims, 2 Drawing Figures ADJUSTABLE INDUCTION COIL FOR ZONE MELTING OF SEMICONDUCTOR RODS CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part application of my copending U.S. Ser. No. 309,420, now US. Pat. No. 3,827,017 filed Nov. 24, 1972, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention generally relates to induction coil structures and somewhat more particularly to readily producible and easily adjustable induction coils useful in crusible-free floating melt zone treatment of semiconductor rods.

2. Prior Art My earlier invention as described in US. Ser. No. 309,420 discloses and claims an induction heating coil useful in crucible-free zone melt treatment of semiconductor rods. The coil structure is disassembleable and includes at least two innersections which are connected to one another by a screw means and may include conduits therein for guiding a fluid therethrough for cooling the coil.

An induction heating coil of this type enables the production of semiconductor rods which have a larger outer diameter than the inner diameter of the coil with the crucible-free zone melting technique. The unique structure of coils of this type do not require unthreading of the rod from the coil or pulling or breaking of the rod at the end of the treatment process. This feature is particularly important in the production of dislocation-free silicon monocrystal rods, which frequently require a series of processing cycles.

The induction heating coil previously disclosed by me, has, in at least certain embodiments, a flange attached to an inner convolution or turn of the coil and at least two inner sections which enable one to adjust the inner diameter of the coil to be selectively attachable to the flange by screws. However, this type of structure is somewhat difficult to manufacture.

SUMMARY OF THE INVENTION The invention provides a readily disassembleable and easily producible induction heating coil for use in crucible-free zone melt processing of semiconductor rods.

It is a feature of the invention to provide an induction heating coil comprised of a single or multi-tum coil arrangement and an annularly shaped insert member attached to the innermost turn and extending radially inwardly toward the center of the coil and which includes conduits therein for guiding a heat-exchange medium through the coil. The insert member is composed of at least two elements, one of which is permanently attached to an innermost turn or convolution of the coil and the other of which is selectively attachable to the permanently attached element by a fastening means, such as a bolt and nut combination. The end face surface of the elements which contact one another during attachment are arranged so that they lie perpendicularly to the plane of the coil.

It is a further feature of the invention to provide upstanding arm-like flanges composed of a conductive material at the outer peripheral areas of the end face surfaces of the insert elements for connecting the elements with one another. In a preferred embodiment, the arm-like flanges are composed of silver-plated brass and are attached to an element by a hard solder.

The coil structures of the invention are easily manufacturable and are well suited for the production of silicon monocrystal rods by the crucible-free zone melting process in a continuous operation.

These and other features, objects and advantages of the invention will become manifest to those skilled in the art upon an inspection of the following description and accompanying drawings which illustrate an exemplary embodiment of a structure manufactured in accordance with the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a coil structure incorporating the principles of the invention; and

FIG. 2 is a partial perspective end view of an element in a coil structure constructed in accordance with the principles of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, an induction heating coil 20 consists of a current conductive loop of at least a single turn arranged in a given plane and includes an insert member 20a which extends radially inwardly toward the center C of the coil 20. The coil is preferably composed of a metal selected from the group consisting of silver, copper and mixtures thereof.

The insert member 20a includes at least two compo nent elements 3 and 7. Element 3 is an annularly shaped portion having permanently attached coil turns 4 and 5 and a conductive terminal 6. Element 7 is an annularly shaped portion which has a permanently attached conductive terminal 8. The terminals 6 and 8 are hollow and may be connected to a suitable source of electrical potential to establish an electric current within the coil. The terminals 6 and 8 may also be connected to a source of a heat-exchange medium, for example, water, and to a sink thereof, respectively. As will be seen, the coil 10 is provided with two convolutions or turns 4 and 5 and is preferably composed of a metal, such as silver. More or less, convolutions may also be provided as desired.

The annularly shaped portions or elements 3 and 7 have first end face surfaces 9 and 10 respectively which contact one another in assembly, as shown. A pair of upstanding arm-like flanges 11 and 12 respectively are soldered to outer peripheral areas of insert portions 3 and 7 respectively, so that on assembly of the coil when the end face surfaces 9 and 10 are brought into contact with one another, the flanges 11 and 12 may be joined to one another by a fastening means 17, such as a bolt and nut combination. This arrangement provides good electrical contact between portions 3 and 7. Preferably, the arm-like flanges 11 and 12 are composed of a silver-plated brass and are joined to their respective insert portion by a hard solder.

The first end face surfaces 9 and 10 of portions 3 and 7 respectively, are arranged to extend perpendicularly to the plane of coil 20. This feature renders the shown structure easily manufacturable and assembleable. The portions 3 and 7 also have second end face surfaces and respectively, which remain spaced from one another in assembly so as to provide an operational coil and prevent a short circuit or the like. One of the portions 3 and 7, say portion 3, is permanently joined to an innermost end of inner coil turn 4, as by a hard solder, and the other portion 7 is joined to the first portion during assembly.

The assembly of a coil structure about a semiconductor rod mounted on a support means is very simple. with portion 7 removed, the coil is mounted to encompass an axial portion of the rod and then the portion 7 is inserted and merely connected to portion 3.

As best seen in FIG. 2, a conduit is provided through portion 3, and of course, similarly through portion 7 (not shown) for guiding a heat-exchange medium, such as water, about insert member a. A rubber O-ring seal 16 is provided about the periphery of conduit 15 at the end faces 9 and, of course, similarly at face 10 (not shown) to prevent leakage of the heatexchange medium. Also as shown at FIG. 2, opposite ends of the upstanding arm-like flange 11 are provided with suitable apertures 13 and 14 for receiving a fastening means therethrough. Of course, similar apertures are also provided on opposite ends of arm-like flange 12.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

I claim as my invention:

1. An induction heating coil for use in crucible-free zone melt treatment of semiconductor rods comprising a current conducting loop of at least a single turn arranged in a given plane and an insert member extending radially inwardly from said turn, said insert member being composed of at least two annularly shaped portions, one of said portions being permanently attached to said conductive loop, and the other of said portions being permanently attached to a terminal to form a conductive path, each of said portions having an end face in contact with an adjacent end face of another portion, said end faces of the portions being disposed perpendicularly to said plane of the turn, fastening means separably attaching said end faces, and a conduit forming a conductive path through said conducting loop and said annularly shaped portions of said insert for guiding a heat exchange medium therethrough.

2. In an induction heating coil as defined in claim 1 wherein said end faces of the annularly shaped portions are provided with upstanding arm-like flanges along their outer peripheral areas for connecting said portions with one another.

3. In an induction heating coil as defined in claim 2 wherein said arm-like flanges are composed of silverplated brass and are attached to an annularly-shaped portion by a hard solder.

4. In an induction heating coil as defined in claim 3 wherein said loop is formed of a tube composed of a metal selected from the group consisting of copper, silver and mixtures thereof.

a: a: a: 

1. An induction heating coil for use in crucible-free zone melt treatment of semiconductor rods comprising a current conducting loop of at least a single turn arranged in a given plane and an insert member extending radially inwardly from said turn, said insert member being composed of at least two annularly shaped portions, one of said portions being permanently attached to said conductive loop, and the other of said portions being permanently attached to a terminal to form a conductive path, each of said portions having an end face in contact with an adjacent end face of another portion, said end faces of the portions being disposed perpendicularly to said plane of the turn, fastening means separably attaching said end faces, and a conduit forming a conductive path through said conducting loop and said annularly shaped portions of said insert for guiding a heat exchange medium therethrough.
 2. In an induction heating coil as defined in claim 1 wherein said end faces of the annularly shaped portions are provided with upstanding arm-like flanges along their outer peripheral areas for connecting said portions with one another.
 3. In an induction heating coil as defined in claim 2 wherein said arm-like flanges are composed of silver-plated brass and are attached to an annularly-shaped portion by a hard solder.
 4. In an induction heating coil as defined in claim 3 wherein said loop is formed of a tube composed of a metal selected from the group consisting of copper, silver and mixtures thereof. 